The present invention relates to scroll type fluid machinery suitable to be used in air compressors, vacuum pumps, and the like.
In general, as one of scroll type fluid machinery, for example, a scroll type compressor in which an orbiting scroll performs an orbiting motion with respect to a fixed scroll by means of a drive source such as a motor to thereby compress air is known (for example, refer to Japanese Utility Model Application Laid-open No. (SHO)58-124692).
Such a conventional scroll type compressor comprises a substantially cylindrical casing, a fixed scroll provided on the casing and having a spiral wrap portion extending from a front surface of an end plate, and an orbiting scroll opposed to the fixed scroll within the casing and having a spiral wrap portion extending from a front surface of an end plate.
The wrap portion of the fixed scroll and the wrap portion of the orbiting scroll are disposed in an overlapped relationship with each other so that a plurality of compression chambers are defined between the wrap portions. Further, a rotary shaft rotated by the drive source is provided within the casing and is rotatably supported by a main bearing disposed within the casing.
Further, the rotary shaft is provided at its leading end with a crank portion eccentric radially from the rotary shaft by a predetermined eccentric amount, and the crank portion is connected to the orbiting scroll via an orbit bearing or the like. In a compressing operation, when the rotary shaft is rotatingly driven, the orbiting scroll performs an orbiting motion around an axis of the rotary shaft with a predetermined orbiting radius, with the result that the air is compressed in the compression chambers defined between the fixed scroll and the orbiting scroll.
On the other hand, a counter weight for achieving weight balance between the counter weight and the orbiting scroll performing an orbiting motion is attached to the drive shaft, and this counter weight is disposed on a radially opposite side of the center of the rotary shaft from the center axis of the orbiting scroll.
Further, the orbiting scroll and the counter weight are spaced apart from each other in the axial direction of the rotary shaft with the interposition of the main bearing and the orbit bearing. As a result, when the orbiting scroll and the counter weight are rotated around the rotary shaft, centrifugal forces applied to these elements act as an external force (moment force) tending to tilt the rotary shaft obliquely.
Thus, in the conventional art, a sub weight is attached to the drive shaft so that the moment force tending to tilt the rotary shaft is cancelled by the sub weight. In this case, the sub weight is spaced apart from the counter weight in the axial direction and is disposed on a radially opposite side of the rotary shaft from the counter weight.
By the way, in the above-mentioned conventional art, it is designed so that the rotary shaft of the compressor is rotatably supported by the main bearing and the counter weight and the sub weight are attached to the rotary shaft on axially opposite sides thereof with the interposition of the main bearing.
However, when the compressor is assembled, parts such as the counter weight, sub weight and main bearing must be assembled to the outer periphery of the rotary shaft separately. In addition, in the assembling operations of the counter weight and the sub weight, assembling positions of these weights must be set or adjusted so that the counter weight is disposed on the radially opposite side of the center of the rotary shaft from the center axis of the orbiting scroll and the sub weight is disposed on the radially opposite side of the rotary shaft from the counter weight (that is to say, the sub weight is disposed on the same side as the center axis of the orbiting scroll).
Thus, in the conventional arts, for example, the assembling structures of the rotary shaft, counter weight, sub weight, main bearing and the like are complicated, and, since it takes a long time to assemble these parts with predetermined positional relationships, there arises a problem that working efficiency and productivity are lowered.
The present invention has been made in view of the above-mentioned conventional art problems, and an object of the present invention is to provide a scroll type fluid machine in which an assembling structure of a rotary shaft, a main bearing, a counter weight, a sub weight and the like can be simplified and a whole assembling operation for these parts can be performed efficiently.